70w metal hallide floodlight

[i=p/u]

Just redo you calcs for the load and cable length , you know quick fix is £100 a flood from jcc, 30w =300w equivalent

 

[plugsandsparks]

Even cheaper is a couple or 4 off 36W CF floodlights, last ones i put up were £25 a piece, cope better with the voltage dips you are getting.

 

[Nivag316]

Try firstlightdirect.com. Look under 25Watt-R7s-Low-Energy-Replacement-118mm-Long-Warm-White_A105GG.asp. Also available from Newey and Eyre for £10ish